Function count

datafusion/expr/src/test/function_stub.rs:70–79

(expr: Expr)

create_func!(Count, count_udaf);

pub fn count(expr: Expr) -> Expr {
    Expr::AggregateFunction(AggregateFunction::new_udf(
        count_udaf(),
        vec![expr],
        false,
        None,
        vec![],
        None,
    ))
}

create_func!(Avg, avg_udaf);